Smokeless powder



Patented Oct. 14, 1947 Ernst Berl and Walter George Berl, Pittsburgh, Ia.; Walter G. Berl as executor of Ernst Berl,

deceased N Drawing.

4 Claims.

Until now two types of smokeless powders have been used for militaryandcivilian purposes. One category is composed of mixtures of cellulosenitrates (nitrocelluloses) with nitrogen contents from 12.3 up to 13.6%.Those mixtures contain completely or partly ether-alcohol solublecollodionwools (12.0-12.6% nitrogen) plus a certain amount ofether-alcohol insoluble guncotton (13.0-13.6% nitrogen). They can beobtained with mixed acids composed of nitric acid, sulphuric acid,water. They have to undergo a stabilizing process. These mixtures ofcollodion wool and guncotton are treated with etheralcohol. The etheralcohol-insoluble guncotton fibers are imbedded in the gel resultingfrom ether-alcohol-soluble collodion wool. In this way one can getbrisant smokeless powders because the non-dissolved guncotton fibersburn with greater speed than the homogeneous colloid formedfromethenalcohol-soluble collodion wool. Other smokeless powders of thistype are made from guncotton (13.0-13.3% N) by complete gelatim'zationwith acetone. They represent the so-called mild smokeless powder type.

A second class of smokeless powders is produced by a mixture ofcellulose nitrate (nitrocellulose) with .glycerine trinitrate(nitroglycerine) with or without glycol dinitrate (nitroglycol). Inadding the liquid nitric acid esters of organic alcohols to solidcellulose nitrates, one raises the nitrogen content, and, therefore, theoxygen content .present as NOz-oxygen (active oxygen). .In this way itis possible to obtain smokeless .powder withmore energy and betterballistic .properties than has been obtained until now with purecellulose nitrate smokeless powders with a collodion wool basis.

Those glycerinetrinitrate (glycol dinitrate)- cellulose nitratesmokelesspowders can be produced without using a common volatile solvent for theused lowernitrated cellulose nitrates and glycerine trinitrate (glycoldinitrate) Then the ballistites result which are ballistically stable.For those smokeless powders cellulose nitrates of the collodion type(with maximum nitrogen content of 12.6%) have to be used. At elevatedtemperatures and pressure, they form with the nitrated aliphaticalcohols (glycerine trinitrate and glycol dinitrate) a gelatine. Thefiber structure of the cellulose nitrate in this gel is com I pletelydestroyed. In view of the very hot flames produced by smokeless powdersof this type containing larger amountsup to 50%-of glycerine trinitrate(glycol dinitrate), usually the quantity pf those liquid nitric acidesters of aliphatic j Application February 26, 1942, Serial No. 432,482

2 alcohols has to be reduced to 20 or 25%. Then the completegelatinization of cellulose nitrate (nitrocellulose) fibers at elevatedtemperature.

and elevated pressure without using volatile solvents for both esters israther dificult to carry out. Many accidents happen then unless largerquantities of stabilizers Which, like derivatives of urea, such asdiethyl diphenyl urea, urethane, etc., in molten state are solvents forcollodion wools are added. By this additional material the ballisticproperties of such a smokeless powder are reduced.

In using a common solvent, for instance acetone, or guncotton(alcohol-ether-insoluble higher nitrated cellulose) and for glycerinetrinitrate (glycol dinitrate) the use of higher nitrated material(12.7-13.3%N) is possible. Those smokeless powderscorditescan beproduced without greater danger. They have the disadvantage that thenecessary elimination of the used volatile solvent (mostly acetone)presents sometimes dangerous complications. The resulting cordites areoften ballistically unstable. They retain larger quantities of solvents,lose those during storage, and after a longer period of storage becomemore brisant.

We have found that stable cellulose nitrates whichcan be produced fromcellulose with mixtures of water-free nitric acid and phosphoric acid(orthoand metaphosphoric acid) containing several percent of freephosphoric acid anhydride, called superphosphoric acids, or thosecellulose nitrates which produced from cellulose with mixtures ofglacial acetic acid and 100% nitric acid without or with a certainamount of either acetic anhydride or phosphoric acid anhydride,according to the U. S. patent application 385,580, filed March 27, 1941,of Ernst Berl (now U. S. Patent No. 2,384,415 of September 4, 1945), canbe used with great advantage for the production of smokeless powders.

' We have furthermore found that those highest nitrated cellulosenitrates can be produced from already nitrated lower cellulose nitratesobtained by'nitration with mixed acids composed of sulphuric acid,nitric acid and water by additional nitration with mixed acids composedof waterfree nitric acid and superphosphoric acids, or glacial aceticacid, with or without addition of acetic anhydride or phosphoric acidanhydride.

These new types of pure cellulose nitrate smokeless powders containpractically the same amount of nitrogen as those smokeless powderscomposed of -76% of collodion wool with I shows the nitrogen content ofmixed cellulose nitrate-glycerine trinitrate smokeless powders wherebycellulose nitrates with different nitrogen contents and dilferent ratiosbetween cellulose nitrate and glycerine trinitrate are used.

Smokeless powders made from:

70 parts cellulose nitrate with 12% nitrogen content and 30 partsglycerine trinitrate with 18.5% nitrogen content contain 13.9% nitrogenand 31.8% oxygen.

'70 parts cellulose nitrate with 12.6% nitrogen content and 30 partsglycerine trinitrate with 18.5% nitrogen content contain 14.35% nitrogenand 32.8% oxygen.

'75 parts cellulose nitrate with 12% nitrogen content and 25 partsglycerine trinitrate with 18.5% nitrogen content contain 13.62% nitrogenand 31.2% oxygen.

75 parts cellulose nitrate with 12.6% nitrogen content and 25 partsglycerine trinitrate with 18.5% nitrogen content contain 14.1% nitrogenand 32.2% oxygen.

80 parts cellulose nitrate with 12% nitrogen con- 7 tent and 20 partscellulose glycerine trinitrate with 18.5% nitrogen content contain 13.3%nitrogen and 30.4% oxygen.

80 parts cellulose nitrate with 12.6% nitrogen content and 20 partsglycerine trinitrate with 18.5% nitrogen content contain 13.8% nitrogenand 31.5% oxygen.

One sees from these figures that pure cellulose nitrate smokelesspowders produced from cellulose nitrates with nitrogen contents up to13. and 14.0% and oxygen contents between 31.8% and 32.2% equal orsurpass the nitrogen and the active oxygen content of most of thosesmokeless powders made as ballistite powders from collodion wools andglycerine nitrate.

These new, pure cellulose nitrate (nitrocellulose) smokeless powderswith ballistic performances which have not been obtained up to this timewith other pure cellulose nitrate smokeless powders by using highestnitrated cellulose nitrates produced with phosphoric or glacial aceticacid nitration processes present many advantages over the mixedcellulose nitrate glycerine trinitrate (glycol .dinitrate) smokelesspowders.

The advantages of the production of smokeless powders made from highestnitrated cellulose nitrates alone are manifold. For their productiononly one operation is necessary-the nitration of cellulose. Thisnitration can be carried out in very short time intervals of a fewseconds or minutes at room temperature. The removal of the spent acidand the stabilization of the resulting highest nitrated cellulosenitrates by repeated hot extraction with swelling but not thesecellulose nitrate dissolving agents like strong methylor ethyl-alcohol,best close to their boiling points, can also be carried out in veryshort time intervals. Furthermore, it is not necessary to pulp thecellulose nitrate fiber in order to carry out this stabilizationprocess. Phosphoric acid and acetic acid do not form mixed esters withnitrated celluloses as is the case with the use of mixed acidscontaining sulphuric acid. Then, as is known, dangerous cellulosenitrato-sulfates are formed. They are difiicult to remove so that stablecellulose nitrates may be obtained. The

pulping which has to be carried out in the normal stabilization processwhen sulphuric acid containing mixed acids are used requires time. Thecosts for power for this cutting of the hardened cellulose nitrate fiberare rather high and the mechanical losses, due to the shortening of thefibers, are relatively great. All these inconveniences are eliminated bythe special nitration processes producing longer fibers of highestnitrated cellulose without their pulping in order to eliminate bound orstrongly adsorbed sulphuric acid.

This highest nitrated material is practicall insoluble in methanol andethanol; therefore, the yield after stabilization by hot extraction withthese alcohols is high. Furthermore, it is not necessary to useafterwards a special dehydration operation for the removal of water fromwet cellulose nitrates stabilized with the older stabilization processesby treatment with acidified and alkaline water. This dehydration processneeds time and lowers the yield.

The production of any geometric form for smokeless powders made from thihighly nitrated cellulose plus stabilizers, and other additionalmaterial for cooling the explosion flames, such as urea, nitroguanidine,etc., and optical compensation of the yellow-red combustion gases, suchas potassium salts, can be made with the help of acetone and itshomologues. Stabilizers, like diphenylamine or substituted ureacompounds, such as diethyl diphenylurea, due to the strongly hydrophobicnature of this highest nitrated material, are retained with strongforces. The same is true for added aromatic nitro compounds like TNT anddinitrotoluene or dinitrobenzene. This fact together with the perfectstabilization by using swelling but not dissolving agents, like methanoland ethanol, allows the production of smokeless powders of until nowunattained stability.

One can destroy the fiber structure of these fibrous highly nitratedcellulose nitrates by subjecting suspensions of dehydrated, highlynitrated cellulose fibers together with non-solvents, likeether-alcohol, methanol, mixtures thereof, or mixtures with acetone andhigher ketones to low temperature, down to C. The lowering of thetemperature causes the complete destruction of the fiber structure underformation of a perfectly gelatini-zed material. In bringing thetemperature up to room temperature, or temperatures up to the boilingpoint of the used solvents,

the formation of very viscous gels takes place which can be transformedby higher temperature and pressure into any geometric form.

Highly nitrated cellulose fibers insoluble at room temperature in theused solvents or solvent mixtures introduced at room temperature in thisgel obtained by the aforementioned treatment at low temperature remaininsoluble. One gets a gel in which the non-attacked, highly'nitratedcellulose fibers are imbedded. After elimination of the solvent byevaporation or by extraction, those non-dissolved fibers remainundissolved. In this way one gets a brisant smokeless powder with untilnow unknown properties.

Therefore, one can produce in this way mild smokeless powders wherebythe whole amount of highly nitrated cellulose fibers is converted into agel under complete destruction of the fiber structure. One can producealso smokeless powders with different ratios between this gel andhighest nitrated cellulose fibers with conserved fiber structure. Thespeed of combustion in the arms can therefore be regulated at will.

The removal of the volatile solvent from the formed smokeless powder canbe carried out by drying it in warm, non-inflammable gas free of or poorin oxygen. The drying can be carried out in counter current so that thealready nearly dry smokeless powder comes in contact with warmoxygen-free (poor) gas containing no solvent vapors. The non-combustiblegas, for instance flue gas, or nitrogen, or carbon dioxide, alreadycharged with solvent vapors, comes in contact with the fresh smokelesspowder containing larger amounts of not yet removed solvents. The dryingcan be carried out also in parallel stream. The fresh smokeless powdertravels in the same direction as the warm drying gases. The last amountsof the solvent are retained by the smokeless powder with rather greatforce. They can be removed by systematic treatment with watery solutionsof swelling but not dissolving substances, for example, alcohol-watersolutions or dioxanewater solutions, using first solutions with a higherpercentage of the organic non-solvent, for example alcohol, and at theendsolutions containing no organic solvent, for example alcohol ordioxane, at all. One can add to these alcohol solutions stabilizers andsubtances which influence the speed of combustion, such as guanidine, sothat in this way a kind of progressively burning powder could beobtained.

The production and use of smokeless powders with highestnitrogen-containing cellulose nitrate content present further greatadvantages over the mixed cellulose nitrate-glycerine trinitrate (glycoldinitrate) smokeless powders. It is known that the latter cannot bedried at somewhat higher temperatures; this in view of the volatility ofthe glycerine nitrate (glycol nitrate) which easily condenses in pureform on cooler places. It may become unstable and may be the source ofexplosions. Furthermore, one cannot treat those mixed cellulosenitrate-glycerine trinitrate powders during a long time with water inorder to remove the last amounts of volatile solvents, especially iflower nitrated cellulose nitrates (12.0-12.6% N) with free hydroxylgroups are used. Then water displaces the otherwise strongly adsorbedglycerine trinitrate (glycol dinitrate) and causes therefore a change inthe composition of the smokeless powder.

The new, pure cellulose nitrate smokeless powders, due to their stronghydrophobic nature, are practically insensitive toward humidity.Smokeless powders made from cellulose nitrates with Example 1 Cellulosenitrate with 13% nitrogen content produced with mixed acids composed ofsulphuric acid, nitric acid and water is treated with mixed acidscomposed of water-free nitric acid and superphosphoric acid(pyrophosphoric or metaphosphoric acid) at room temperature or somewhatincreased or lower temperature. The

nitrogen content after this additional nitration and afterstabilizationwith strong alcohol is raised to 13.9-14.0% nitrogen. Tothe resulting wet mass acetone and 1-8% of centralite-symmetric diethyldiphenyl urea (melting point 71.5 C.) are added. Small amounts ofpotassium salts for the optical compensation may be added. Thepreparation of smokeless powders of any geometric form has to be carriedout according to known processes. The resulting smokeless powder has thesame ballistic properties as ballistite to which the same amounts ofcentralites and potassium salts have been added. The new smokelesspowder is not influenced in its ballistic activity by the humidity ofthe air and by a treatment with water. Ballistite submitted to the sameconditions would adsorb, according to the humidity of the air, larger orsmaller quantities of water and by a treatment with liquid water wouldlose glycerine trinitrate and would change its ballistic properties.

Example 2 Cellulose nitrate with 13.95% nitrogen content produced by thedirect nitration of cellulose. with water-free nitric acid andsuperphosphoric acid (pyroor metaphosphoric acid) or according to,Example 1 is extracted and stabilized with hot methanol. Methanol doesnot dissolve the fiber at room or higher temperature. To this nowexcellently stabilized material which has retained its fibrous form moremethanol is added if necessary. This suspension is submitted to lowtemperature (50 0.). Then the fiber structure of the nitrated cellulosedisappears completely and a homogeneous gel is formed. To this gelstabilizers, furthermore substances which lower the temperature ofexplosion, like nitroguanidine, may be added. The mixture, best undercontinu ous mixing, has to be brought to room temperature. Its viscosityincreases. Under pressure and heat the formation of smokeless powder ofany geometric form can be carried out.

Example 3 The first steps of the production of smokeless powder asdescribed in Example 2 are carried out. To this gel without fiberstructure at room temperature unpulped or pulped fibrous cellulosenitrate dehydrated and stabilized by methanol with nitrogen contentsfrom l2.8-14% N is added. In appropriate kneaders a uniform suspensionof these fibers in this gelatine is made. Between 10 and 400% of thefibrous material may be added to the gel; this based on the amount ofcellulose nitrate of which the fiber structure has been destroyed.

Example 4 Instead of using methanol, as described in Examples 2 and 3,ether-alcohol may be used as a solvent for this highly nitratedguncotton which is ether-alcohol insoluble at room temperature. At thelow temperature (-20 to -70 C.) a complete gelatinization under loss offiber structure of this highest nitrated guncotton material takes place.One can add, as is described in Example 3, to this homogeneous gel atroom temperature fibrous cellulose nitrate (with 12.8-14% N) in order toget a more brisant smokeless powder.

Example i To methanol, as is described in Examples 2 an Example 6Acetone as used in Examples 1 and 5 may be partly or wholly substitutedby higher aliphatic ketones like methyl-ethyl ketone, or methyl-propylketone or di-isobutyl ketone.

We claim:

1. Hydrophobic single base smokeless powder produced from a stablecellulose nitrate with nitrogen contents from 13.8 to 14.0%, comprisinga gel without fiber structure in which nitrated cellulose fibers withnitrogen contents up to 14.0% and'the same solvent properties as thecellulose nitrate of said gel are imbedded.

2. Hydrophobic single base smokeless powder produced from a stablecellulose nitrate with nitrogen contents from 13.8 to 14.0% according toclaim 1 With'the addition of an appropriate stabilizer.

3. Hydrophobic single base smokeless powder produced from a stablecellulose nitrate with nitrogen contents from 13.8 to'14.0% according toclaim 1 with the addition of a cooling agent.

4. Hydrophobic single base smokeless powder produced from a stablecellulose nitrate with nitrogen contents from 13.8 to 14.0% according toclaim 1 with the addition of a substance capable of opticallycompensating the ellow-red combustion flames.

ERNST BERL.

WALTER GEORGE BERL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,125,880 Berl Aug. 9, 19381,938,176 Dreyfus Dec. 5, 1933 1,884,802 Miles Oct. 25, 1932 781,926Wiley Feb. 7, 1905 2,230,848 Regestein Feb. 4, 1941 2,153,331 Kunz Apr.4, 1939 2,028,990 Olsen Jan. 28, 1936 1,978,071 York Oct. 23, 19341,978,070 York Oct. 23, 1934 FOREIGN PATENTS Number Country Date 632,614France Oct, 10, 1927 483,474 Great Britain Apr. 19, 1938 269,529 GreatBritain Apr. 8, 1927 OTHER REFERENCES Allens Comm. Organic Analysis, 5thed., vol. 3, p. 598,

Explosives, (1925) Marshall, vol. 1, Phila, 1917, pp. 135437.

